Toroidal type automatic transmission for motor vehicles

ABSTRACT

Even in the case where a driver switches a select lever from D range to N range and returns it back to D range during the running of a vehicle, a speed change control device prevents the operation of sudden speed change caused by a difference between a transmission input rotational speed and the actual input rotating speed of a toroidal transmission unit while in the N range. Accordingly, an automatic transmission comprises a forward-reverse switching mechanism, an impelling mechanism and a toroidal transmission unit which are sequentially arranged from the driving source side of a vehicle, and further comprises a speed change control device for controlling the operation of the above. A notch as a rotational speed signaling section is provided on the outer periphery of a loading cam, for example, among rotating members in the area from an output member of the above forward-reverse switching mechanism to an input disc of the above toroidal transmission unit, and the notch is detected by a rotation sensor arranged in the vicinity of the outer periphery to detect the rotational speed of the loading cam and input the same to the speed change control device.

FIELD OF THE INVENTION

The present invention relates to an automatic transmission for avehicle. It particularly relates to the automatic transmissioncomprising a toroidal-type continuously variable transmission includinga torque converter, a forward-reverse switching mechanism, a impellingmechanism and a toroidal transmission unit which are sequentiallyprovided from the driving source (engine) end of a vehicle, and furthercomprising a speed change control device for controlling speed changeratio and forward-reverse switching.

BACKGROUND OF THE INVENTION

A toroidal type continuously variable transmission as an automatictransmission for a vehicle is described in JP-A-2-163562. This toroidaltype continuously variable transmission has two toroidal transmissionunits in tandem, and is provided with a forward-reverse switchingmechanism disposed on the preceding stage side of the toroidaltransmission units.

In order to control the speed change ratio of the toroidal typecontinuously variable transmission, the above speed change controldevice obtains the ratio of the input rotational speed of thetransmission as detected by a rotating speed sensor, to the outputrotational speed, and changes the tilting angle of a power roller of thetoroidal transmission unit according to the engine load, the vehiclespeed and so on when the automobile is in motion to change the ratio ofthe output rotation to the input rotation, that is, the speed changeratio.

In such circumstances, the sensor for the input rotational speed of thetransmission detects the output rotational speed of the torqueconverter. Accordingly, there is a difference between the transmissioninput rotational speed which the sensor inputs into the speed changecontrol device for speed change control and the actual input rotationalspeed of the toroidal transmission unit.

However, the sensor for detecting the input rotational speed sometimescan not accurately detect said speed of the transmission under certainconditions.

When a driver switches the operating lever of the continuously variabletransmission, from a drive range (D range) to a neutral range (N range)that is to say, puts the automobile in neutral during running, theforward-reverse switching mechanism becomes free in the N range, so thatthe rotation is not transmitted from the output shaft of the torqueconverter to the input shaft of the toroidal transmission unit.Accordingly, though the rotation of the output shaft of the torqueconverter corresponds to the engine rotational speed, the input shaftrotational speed of the toroidal transmission unit depends on therotation of the output shaft at that time. Therefore it corresponds tothe rotational speed corresponding to the vehicle speed and the speedchange ratio.

In such cercumstances, the sensor for the input rotational speed of thetransmission detects the output rotational speed of the torqueconverter. Accordingly, there is a difference between the transmissioninput rotational speed which the sensor inputs into the speed changecontrol device for speed change control and the actual input rotationalspeed of the toroidal transmission unit.

When the driver switches the select lever again from N range back to Drange ie. puts the automobile back into drive, in such a runningcondition that an input rotational speed difference results, the speedchange control device determines the speed change ratio according to theinput rotational speed when in the N range, which is different from theactual input shaft rotational speed of the toroidal transmission unitimmediately after the above switching.

Therefore the transmission applies a speed change ratio determinedaccording to rotational speed data different from the actual inputrotational speed. Therefore the toroidal transmission unit is forced toconduct a sudden speed change operation, which results in thedisadvantage that a comparatively large speed change shock is produced.

A methods for overcoming this disadvantage, is to dispose theforward-reverse switching mechanism not on the preceding stage side(input side) of the toroidal transmission unit, but to the subsequentstage side in order to connect the output side of the torque converterand the input side of the toroidal transmission unit to each other. As aresult, the input rotational speed detected by the sensor alwayscorresponds to the input shaft rotational speed of the toroidaltransmission unit.

However, as the arrangement of the forward-reverse switching mechanismis changed in such a way, during normal running, the large torquerotation decelerated by the toroidal transmission unit is always appliedto the forward clutch in the forward-reverse switching mechanism andreverse brake. These members need to have high durability, which resultsin the disadvantage that it is necessary to increase their capacity andthe size.

It is, accordingly, an object of the present invention to prevent aspeed change shock by always accurately detecting the actual input shaftrotational speed of the toroidal transmission unit and conducting speedchange control according to this accurate detected rotational speed.

It is another object of the present invention to accurately detect theinput rotational speed of the toroidal transmission unit withoutchanging the arrangement of the forward-reverse switching mechanism tothe subsequent stage side of the toroidal transmission unit.

SUMMARY OF THE INVENTION

In order to achieve the foregoing objects, the automatic transmissionfor a vehicle of the present invention comprises a toroidal typecontinuously variable transmission including a forward-reverse switchingmechanism, an impelling mechanism and a toroidal transmission unit whichare sequentially provided from the driving source end of the vehicle,and a speed change control device for controlling the operation of thetransmission. A rotational speed signalling section is provided on oneof the rotating members, which are connected to each other in the areafrom the output member of the forward-reverse switching mechanism to theinput disc of the toroidal transmission unit, regardless of presence orabsence of rotation transmission in the forward-reverse switchingmechanism, an input rotational speed detecting part fitted to thetransmission case side is positioned in the vicinity of the outerperiphery of said rotational speed signalling section, and the inputrotational speed detecting part detects the rotational speed of therotating member provided with the rotational speed signalling section tobe input to the speed change control device.

In the toroidal type continuously variable transmission for a vehicle ofthe present invention, even in the case where a driver switches theselect lever of the automatic transmission from D range to N rangeduring the running of a vehicle and the rotation is not transmitted tothe forward-reverse switching mechanism, the rotational speed of one ofthe rotating members in the area from the output member of theforward-reverse switching mechanism to the input disc of the toroidaltransmission unit, that is, the rotational speed which agrees with theinput shaft rotational speed of the toroidal transmission unit isdetected by the input rotational speed detecting part to be input to thespeed change control device. Therefore the actual rotational speed inputto the toroidal transmission unit, which is always detected accurately,continues to be input to the speed change control device while drivingin the N range.

Accordingly, even if the driver switches the select lever of theautomatic transmission from N range back to D range, the speed changecontrol device controls the forward-reverse switching mechanism totransmit the rotation, controls the speed change ratio of the toroidaltransmission unit on the basis of the actual input rotational rotatingspeed of the toroidal transmission unit while in the N range. Thereforethe toroidal transmission unit is kept from performing sudden speedchange operation and no speed change shock results.

In the present invention, the rotating member provided with therotational speed signalling section is a loading cam in the impellingmechanism, and the rotational speed signalling sector may be provided onthe outer peripheral part of the loading cam. The loading cam of theimpelling mechanism, to which the output rotation of the forward andreverse switching mechanism is input, transmits the rotation to theinput disc of the toroidal transmission unit through a cam roller androtates substantially in unison with the input disc. Therefore the outerperipheral part of the loading cam expresses the maximum peripheralspeed of the loading cam. The pitch of the signal section can be madesmaller, so that the actual input rotational speed of the toroidaltransmission unit can be detected accurately.

Further, in the present invention, the rotating member provided with therotational speed signalling section may be a cam roller holder in theimpelling mechanism, and the rotational speed detecting part may beprovided on the outer peripheral part of the cam roller holder. The camroller holder of the impelling mechanism is also rotated substantiallyin unison with the cam roller. Subsequently, the input disc also rotateswhen the loading cam transmits the output rotation of theforward-reverse switching mechanism through the cam roller to the inputdisc of the toroidal transmission unit, so that the actual inputrotational speed of the toroidal transmission unit can be detectedaccurately.

Further, in the present invention, when the rotational speed detectingpart is provided on the outer peripheral part of the cam roller holder,the loading cam of the impelling mechanism may have a smaller diameterthan the cam roller holder of the impelling mechanism, and an outerperipheral part provided with the rotational speed signalling section ofthe cam roller holder may be formed in such a manner as to be extendedin the axial direction, surrounding the outer peripheral part of theloading cam. The cam roller holder moves a little in the axial directionof the cam roller when the loading cam presses on the input disc throughthe cam roller with a force corresponding to transmission torque movingthe input disc toward the output disc. Therefore if the outer peripheralpart provided with the rotational speed signalling section of the camroller holder is formed in such a manner as to be extended in the axialdirection as described above, even if the cam roller holder moves in theaxial direction, the input rotational speed detecting part can alwaysdetect the rotational speed of the rotational speed signalling sectionof the cam roller holder accurately. If the outer peripheral part of thecam roller holder is extended in the axial direction, as describedabove, and the loading cam is formed in such a manner as to have asmaller diameter than the cam roller holder and the outer peripheralpart of the loading cam is surrounded with the outer peripheral part ofthe cam roller holder, the outer peripheral part of the cam rollerholder can be extended in the axial direction without any increase inthe radial dimension of the cam roller holder so as to eliminate theneed of increasing the radial dimension of the toroidal typecontinuously variable transmission.

Further, in the present invention, the cam roller holder may have asmaller diameter than the input disc of the toroidal transmission unit.In such a configuration, the radial dimension of the cam roller holderwill not be larger than the radial dimension of the input disc so as toeliminate the need of increasing the radial dimension of the toroidaltype continuously variable transmission.

Further, in the present invention, a rotating member provided with therotational speed signalling section may be an input disc of the toroidaltransmission unit. The rotational speed signalling section may beprovided on the outer peripheral part of the input disc, and therotating member provided with the rotational speed signalling sectionmay be also the output member of the forward-reverse switchingmechanism. For detecting the actual input rotational speed of thetoroidal transmission unit, it is desirable to detect the rotationalspeed of the input disc, so that if there is spatial room in theperiphery of the input disc, and strengthening margins are provided inthe input disc, the rotational speed signalling section may be providedon the outer peripheral part of the input disc.

Further, as an output member such as a pinion carrier or the like is theforward-reverse switching mechanism is always rotated substantially inunison with the input disc, the rotational speed signalling section maybe provided on the output member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a skeleton diagram showing the construction of a toroidal typecontinuously variable transmission for a vehicle according to thepresent invention,

FIG. 2 is a sectional view showing the principal part of one embodimentof a toroidal type continuously variable transmission for a vehicleaccording to the present invention;

FIG. 3 is a front view of a loading cam of the above continuouslyvariable transmission, taken in the direction of an arrow II of FIG. 2;

FIG. 4 is a sectional view showing the principal part of anotherembodiment of a toroidal type continuously variable transmission for avehicle according to the present invention; and

FIG. 5 is a plan view of a cam roller holder of the above continuouslyvariable transmission, taken in the direction of an arrow IV of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be describedwith reference to the attached drawings.

As shown in FIG. 1 a toroidal type continuously variable transmissionfor a vehicle is, so constructed that two toroidal transmission units 1are arranged in tandem, an impelling mechanism 2 is provided at apreceding stage (input side) to the toroidal transmission unit 1, and aforward-reverse switching mechanism 3 is provided at the preceding stageto the impelling mechanism 2.

Each toroidal transmission unit 1 includes coaxially-arranged input andoutput discs 4, 5, and a pair of power rollers 6 clamped between theinput and output discs to transmit power by frictional contact. Thetilting angle of the power roller 6 is changed by a driving mechanism(not shown).

Two toroidal transmission units 1 are arranged back to back, and theirrespective input discs 4 are connected to each other in such a manner asto respectively engage with the torque transmission shaft 7 in therotating direction through a ball spline mechanism 8 and slide in theaxial direction. A pair of output discs 5 arranged back to back to thetwo toroidal transmission units 1 are connected to each other through anoutput shaft 9.

Accordingly, when the input disc 4 is rotated, the power roller 6 isrotated so that the output disc 5 coming into contact with the roller 6is rotated, and the transmission ratio of the rotation varies with thetitling angle of the power roller 6.

The impelling mechanism 2 is adapted to ensure the frictional contactamong the respective input and output discs 4,5 and the power roller 6of two toroidal transmission units 1. A loading cam 10 is arranged onone end part of the torque transmission shaft 7 and a disc spring 11 isarranged on the other end part thereof in such a manner as to bepositioned outside the respective input discs 4 of two toroidaltransmission units 1. A cam roller 12 installed by a disc-like camroller holder mentioned later and is provided between the loading cam 10and the back face of the input disc 4 of the toroidal transmission unit1 adjacent thereto, which is on the left side of the drawing.

An input shaft 13 is connected to the loading cam 10 to be connected tothe forward-reverse switching mechanism 3.

A countershaft 15 is arranged parallel to the output shaft 9, and anoutput gear 14 provided on the output shaft 9 and a counter gear 16provided on the countershaft 15 mesh with each other so that therotation of the output shaft 9 is transmitted to the countershaft 15.The countershaft 15 transmits the rotation to a driving wheel (notshown) through a power transmission system (not shown) such as adifferential gear mechanism for a vehicle or the like.

The forward-reverse switching mechanism 3 includes a planetary gearmechanism. It has a sun gear 17, a pinion carrier 18 connected to theinput shaft 13, an internal gear 19, and pinions 20 rotatably supportedin pairs on the pinion carrier 18, one of which meshes with the sun gear17, the other meshing with the internal gear 19, two forming a pairmeshing with each other. A forward clutch 21 is interposed between thesun gear 17 (a turbine shaft 31 to which the sun gear 17 is connected)and the pinion carrier 18, a reverse brake 23 is interposed between theinternal gear 19 and a transmission case 22, and the forward clutch 21and the reverse brake 23 are controlled to be selectively engaged.

A torque converter 24 is arranged between the forward-reverse switchingmechanism 3 and an engine (not shown) as a driving source of a vehicle,the pump housing 25 side of the torque converter 24 is joined to theoutput shaft of the engine, and the sun gear 17 of the forward-reverseswitching mechanism 3 is joined to the turbine shaft 31 connected to aturbine 26 of the torque converter 24.

In the toroidal type continuously variable transmission, the outputrotation of the engine is transmitted to the forward-reverse switchingmechanism 3 through the torque converter 24. In the forward-reverseswitching mechanism 3, when the forward clutch 21 is in the engagementstate (the reverse brake 23 is released), the sun gear 17 and the pinioncarrier 18 are joined to each other by the forward clutch 21 to transmitthe rotation from the torque converter 24 intact as forward rotation tothe input shaft 13. On the other hand, when the reverse brake 23 is inthe engagement state (the forward clutch 21 is released), the internalgear 19 is fixed to the transmission case 22 by the reverse brake 23,the sun gear 17, the internal gear 19 and the pinion 20 function as aplanetary gear set, as a result, the rotation from the torque converter24 is reversed and transmitted as backward rotation to the input shaft13.

The rotation of the input shaft 13 is transmitted from the loading cam10 through the cam roller 12 to the input disc 4 of the toroidaltransmission unit 1 adjacent thereto on the left side in the drawingfrom the back face thereof. At this time, the loading cam 10 is turnedin a small-degree arc relative to the input disc 4 depending on thetransmission torque, whereby the cam roller 12 is pushed to displace theinput disc 4 in the axial direction in some measure. The axialdisplacement increases the frictional force of the power roller 6clamped between the input disc 4 and the output disc 5.

The rotation of the input disc 4 is transmitted through a ball splinestructure 8 to the torque transmission shaft 7 and further transmittedthrough the ball spline structure 8 to another input disc 4 of thetoroidal transmission unit 1 on the right side in the drawing. By therotation of the input discs 4 of each toroidal transmission unit 1, thepower roller 6 coming into frictional contact therewith is rotatedaround the central axis O, and the rotation is transmitted to the outputdisc 5 coming into contact therewith and further transmitted to theoutput shaft 9.

The rotation of the output shaft 9 is transmitted through the outputgear 14 and the counter gear 16 meshing with each other to thecountershaft 15 and then transmitted through the described powertransmission system of the vehicle to the driving wheels to drive thevehicle forward and backward.

On the other hand, the power rollers 6 of the toroidal transmission unit1 of the right and left are rotated in synchronization with each otherwith a gradient in the direction intersecting perpendicularly to theaxis, the radial positions of the contact parts of the input and outputdiscs 4,5 with the power rollers 6 are changed. Therefore the rotationtransmission ratio is changed with the result that the rotation of theinput shaft 13 varies in a non-step fashion and is transmitted to theoutput shaft 9.

A speed change control device for controlling the speed change operationof the described toroidal type continuously variable transmissionobtains the rotational speed ratio of the input shaft 13 to the outputshaft 9 corresponding to the speed change ratio, that is to say, theinput and output rotational speed ratio of the toroidal transmissionunit 1 from the transmission input rotational speed which is therotational speed of the input shaft 13 and the transmission outputrotational speed detected by the sensor provided on the describedtransmission mechanism of the vehicle, to change the rotation speed tobe transmitted to the output shaft 9 by changing the tilting angle ofthe power roller 6 according to the engine load, the vehicle speed andso on during running, and controls the input and output rotational speedratio in a non-step fashion.

Accordingly, in the present invention, a rotational speed sensor fordetecting the described transmission input rotational speed is installedon a rotating member in an area from the output member of theforward-reverse switching mechanism 3 to the input disc 4 of thetoroidal transmission unit 1.

An actual example is shown in FIG. 2. The cam roller 12 is arranged inthe state of being held by a disc-like cam roller holder 27 between theloading cam 10 and the input disc 4 of the toroidal transmission unit 1adjacent thereto. The input shaft 13 of FIG. 1 is connected to theloading cam 10 to make the same rotation as the output rotation of theforward-reverse switching mechanism 3.

The outside diameter of the loading cam 10 is a little smaller than theoutside diameter of the input disc 4, and the outer peripheral part ofthe loading cam 10 is, as shown in FIG. 3, provided with many notches 10a formed as a rotational speed signalling section at equal spaces in thecircumferential direction.

On the other hand, a rotation sensor 28 functioning as an inputrotational speed detecting part is fixed to the inside of thetransmission case 22 to be opposite to the vicinity of the notch 10 a inthe outer peripheral part of the loading cam 10. The rotation sensor 28detects the passing interval of the notches 10 a in the outer peripheralpart of the loading cam 10 which corresponds to the rotational speed ofthe loading cam 10 on the basis of changes in the magnetic flux, andinputs the detection signal into the speed change control device.Depending on the detection signal, the speed change control device usesthe rotational speed of the loading cam 10, and, in its turn, to theactual input rotational speed of two toroidal transmission units 1 tocontrol the speed change operation of the toroidal transmission units 1.

The loading cam 10 presses the input disc 4 via the cam roller 12, sothat the reaction load is applied to the input disc 4 from the contactpoint with the power roller 6. As the contact point with the powerroller 6 is positioned near the outer peripheral part of the input disc4 when the power roller 6 is tilted to increase speed, it is notdesirable to dispose the cam roller 12 too near the inner peripheralpart of the input disc 4 because a large bending stress is generated inthe input disc 4. Accordingly, in the present embodiment, the basis ofthere considerations, the cam roller 12 is arranged in the middle of theouter peripheral part and the inner peripheral part of the input disc 4,and the outside diameter of the loading cam 10 is made smaller than thatof the input disc 4 so far as the loading cam can presses the cam roller12.

In the toroidal type continuously variable transmission for a vehicle,even if a driver switches the select lever of an automatic transmissionfrom D range to N range during the running of the vehicle so thatrotation is not transmitted to the forward-reverse switching mechanism,the rotational speed of a rotating member, which is the loading cam 10in the present embodiment, in the area from the pinion carrier 18 as theoutput member of the forward-reverse switching mechanism 3 to the inputdisc 4 of the toroidal transmission unit 1, which is joined to be drivenregardless of presence or absence of a rotation transmission in theforward-reverse switching mechanism 3, is detected by the rotationsensor 28 to be input to the speed change control device.

The rotational speed of the loading cam 10 corresponds to the rotationalspeed of the output shaft of the toroidal transmission unit 1 and thespeed change ratio at that time, and this is nothing but the actualinput rotational speed of the toroidal transmission unit 1.

While at this stage, the engine rotational speed is transmitted to thetorque converter 24, however, it is not transmitted to the input shaft13 because the forward-reverse switching mechanism 3 is free.

Thus, the actual rotational speed input to the toroidal transmissionunit 1, which is always detected accurately, continues to be input tothe speed change control device even while in the N range.

Accordingly, even after that, if the driver switches the select lever ofthe automatic transmission from N range back to D range, the speedchange control device controls the forward-reverse switching mechanism 3to transmit the rotation and on the other hand, controls the speedchange operation of the toroidal transmission unit 1 on the basis of theactual input rotational speed of the toroidal transmission unit 1 whilein the N range, so that the toroidal transmission unit 1 is kept fromordering a sudden speed change operation.

According to the present embodiment, even in the case where the driveronce switches the select lever of the automatic transmission from Drange to N range during running of the vehicle, and returns it again tothe D range, it is possible to effectively prevent the generation of aspeed change shock caused by a difference between the transmission inputrotational speed and the actual input rotational speed of the toroidaltransmission unit 1 while in the N range. In this case, it is notnecessary to change the arrangement of the forward-reverse switchingmechanism from the preceding stage side of the toroidal transmissionunit 1 to the subsequent stage side. It is also unnecessary to increasea forward clutch and a reverse brake of the forward-reverse switchingmechanism in capacity and size.

The loading cam 10 of the impelling mechanism 2 is rotated substantiallyin unison with the input disc 4, and notches 10 a as a rotational speedsignalling section are provided on the outer peripheral part of theloading cam 10, whereby the pitch of the notches can be made smaller andthe notches 10 a are detected by the rotation sensor 28 so that theaccuracy of detecting the actual input rotational speed of the toroidaltransmission unit can be heightened.

Another embodiment will now be described by FIGS. 4 and 5.

In the embodiment, as shown in FIG. 4, the outside diameter of theloading cam 10 is made smaller than the outside diameter of the inputdisc 4, the outside diameter of the cam roller holder 27 of theimpelling mechanism 2 is made a little smaller than the outside diameterof the input disc 4, and further the tip part of the outer periphery ofthe cam roller holder 27 is bent at a right angle to be extended in theaxial direction, surrounding the outer peripheral part of the loadingcam 10.

The axially extended cylindrical part is, as shown in FIG. 5, providedwith many notches 27 a as a rotational speed signalling section formedat equal spaces in the circumferential direction. The rotation sensor 28functioning as an input rotational speed detecting part is fixed to theinside of the transmission case 22 to be opposite to the notch 27 a ofthe outer peripheral part of the cam roller holder 27.

The rotation sensor 28 detects the passing interval of the notches 27 aof the outer peripheral part of the cam roller holder 27 correspondingto the rotational speed of the cam roller holder 27 according to thechange in magnetic flux, and inputs the detection signal to the speedchange control device.

Accordingly, similarly to the described embodiment, the rotation sensor28 can always detect the actual input rotational speed of the toroidaltransmission unit 1 accurately.

When the loading cam 10 presses the input disc 4 through the cam roller12 with an impelling force corresponding to the transmission torquemoving the input disc 4 toward the output disc, the cam roller holder 27is moved a little in the axial direction of the cam roller 12.

However, as the notches 27 a are formed on the axially extendedcylindrical part, even if the cam roller holder 27 moves a little in theaxial direction, the rotation sensor 28 can always accurately detect thepassing interval of the notches 27 a of the cam roller holder 27, and inits turn, the rotational speed of the cam roller holder 27.

In extending the tip part of the cam roller holder 27 in the axialdirection, as described above, the loading cam 10 has a smaller diameterthan the cam roller holder 27 and the outer peripheral part of theloading cam 10 is surrounded with the tip part of the cam roller holder27, so that it is not necessary to increase the diameter of the tip ofthe cam roller holder 27. Further, the cam roller holder 27 has asmaller diameter than the input disc 4, so that it is not necessary toincrease the radial dimension of the toroidal type continuously variabletransmission.

This invention is not limited to the described examples. For example, inorder to detect the actual rotational speed of the toroidal transmissionunit, it is desirable to detect the rotational speed of the input disc,so if there is spatial room in the periphery of the input disc, andstrengthening margins are provided in the outer peripheral part of theinput disc, the rotational speed signalling section may be provided onthe outer peripheral part of the input disc. The output member such as apinion carrier or the like of the forward-reverse switching mechanism isrotated substantially in unison with the input disc, so that therotational speed signalling section may be provided on such an outputmember.

Other kinds of sensors may be used as an input rotational speeddetecting part instead of the sensor of the described embodiment adaptedto detect the passing interval of notches according to the change ofmagnetic flux, and though two toroidal transmission units are providedin tandem in the above embodiment, in the continuously variabletransmission of this invention, it is sufficient to provide one toroidaltransmission unit.

What is claimed is:
 1. An automatic transmission for a vehicle,comprising: a toroidal type continuously variable transmission having aforward-reverse switching mechanism, an impelling mechanism and atoroidal transmission unit which are sequentially provided from thedriving source side of the vehicle; and a speed change control devicefor controlling the operation of said transmission, wherein saidimpelling mechanism comprises a loading cam and a cam roller holder,wherein a rotational speed signaling section is provided on one ofrotating members, which are connected to each other, in the area from anoutput member of said forward-reverse switching mechanism to said camroller holder of said impelling mechanism, said one of rotating membersrotating regardless of the presence or absence of the rotationtransmission in said forward-reverse switching mechanism, and wherein aninput rotational speed detecting part, installed on a side of a case ofthe transmission, is positioned in the vicinity of an outer periphery ofsaid rotational speed signaling section, said input rotational speeddetecting part detects a rotational speed of said one of rotatingmembers provided with said rotational speed signaling section and inputsthe detected rotational speed to said speed change control device. 2.The automatic transmission for a vehicle as claimed in claim 1, whereinsaid rotating member provided with said rotational speed signalingsection is said loading cam of said impelling mechanism, and saidrotational speed signaling section is provided on the outer peripheralpart of said loading cam.
 3. The automatic transmission for a vehicle asclaimed in claim 1, wherein said rotating member provided with saidrotational speed signaling section is said cam roller holder of saidimpelling mechanism, and said rotational speed signaling section isprovided on the outer peripheral part of said cam roller holder.
 4. Theautomatic transmission for a vehicle as claimed in claim 3, wherein thediameter of said loading cam of said impelling mechanism is smaller thanthat of said cam roller holder of said impelling mechanism, and theouter peripheral part of said cam roller holder provided with saidrotational speed signalling section is formed in such a manner as to beextended in the axial direction, surrounding the outer peripheral partof said loading cam.
 5. The automatic transmission for a vehicle asclaimed in claim 4, wherein the diameter of said cam roller holder issmaller than that of said input disc of said toroidal transmission unit.6. The automatic transmission for a vehicle as claimed in claim 1,wherein said rotating member provided with said rotational speedsignalling section is an output member of said forward-reverse switchingmechanism.